Re: [Gimp-user] Failed to open NEF files on Ubuntu

["Rick Strong" <rnstrong primus ca>]

Nikon provides 2 free programs for it's NEF files: Capture NX-D and 
ViewNX-i. I use them to import D810 photos and to make changes in post. 
Output to jpg or tif and tweek in GIMP. I don't know how/if they work with 
Ubuntu. Worth a look.

"Capture NX-D is a non-destructive RAW image processing application that 
utilizes a sidecar system to save adjustments for Nikon photographers 
looking to edit and process Nikon .NEF or .NRW files. By using a sidecar 
file, instead of storing changes in the original file, Capture NX-D is 
non-destructive. This means you can always reprocess an image without having 
to undo all of your previous changes."

https://www.nikonusa.com/en/learn-and-explore/a/tips-and-techniques/nikon-capture-nx-d-software.html 
.

RIck S.